While you are reight in much of your logic, you forget the "feel" that people want from tehir camera, some of which translates into real concerns.
The D7000/7100/D600 are all much smaller bodies than the D300/700/800. For some people, me included, they don't feel right. I don't enjoy the tactile sense when holding them.
In real terms, for some people, that small body is a problem, given the size of their hands and fingers. Then the is also the question of balance of a small, light body ad a large lens. Finally, for this post anyway, there is the issue of what buttons, connections, and control layout options you can have with a larger body.
Some people are still wishing for a D4 body with a DX sensor. I think Nikon buried that idea with the D3/D300. However, I think there is a significant demand for a D300 size DX Pro featured camera. Is it the majority of DX shooters? Of course not, but there are likely enough potential buyers to make it worthwhile for Nikon.
I guess we'll see over the balance of this year what cameras are announced and which are dropped from the lineup.